The present invention relates generally to wireless communication systems and, more particularly, to accurate geo-location of ultra wideband transceivers.
Ultra wideband communication systems and devices benefit from the tremendous potential for geo-positional accuracy of ultra wideband technology. As a separate issue, the FCC has recently required all existing cellular technology providers to employ some means of geographically locating all cellular phones for emergency purposes. This initiative has been termed xe2x80x9ce911xe2x80x9d and will be a requirement of future cellular technologies. Thus, it is foreseeable that the same demands will be placed on future ultra wideband devices.
Conventionally, ultra wideband geo-positional information may be obtained by triangulating signals from three separate ultra wideband transmission towers whose fixed position is known. However, it is foreseeable that a mobile ultra wideband device may not always be within range of three fixed transmission towers. In such a situation, the ultra wideband device""s geo-location (i.e., geo-position) may not be determined through the conventional methods.
Thus, it may be appreciated that a geo-location method that takes advantage of other mobile ultra wideband devices of known location to derive the position of the ultra wideband device that is in need of location has a better chance of success in these circumstances.
A system, method and article of manufacture are provided for determining a location of a wireless device in a wireless communication system. In general, an initial request is transmitted to wireless devices having known locations for positioning information so that a location can be determined for a first wireless device having an undetermined location. Those wireless devices with known locations that receive the initial request in turn transmit positioning information to the first wireless device. If positioning information from less than a sufficient number of wireless devices with known location is received by the first mobile wireless device, an additional request is then transmitted for responses from other responding wireless devices. After responses to the request from one or more of these responding other wireless devices are received, communication then occurs with at least a portion of the responding wireless devices to obtain information relating to the distance between the first wireless device and the responding wireless devices it is communicating with. These responding other wireless devices may also respond to the request by polling for its own geo-location from more distant known-location devices thus producing a request that propagates through an ad hoc network. Alternatively, in some circumstances, they may simply provide a distance to the first mobile wireless device. An example of such a circumstance is a lost child carrying the first wireless device and several searchers, each with a responding wireless device. In this example, the searchers are not interested in the geo-position of the child, but in the child""s distance from each of the searchers. In this scenario a local triangulation without a geopositional reference is all that is required to find the child. Thus, a location of the first wireless device is estimated using the information (distance or location) obtained from the responding other wireless devices and the positioning information received from the wireless devices with known locations.
In one aspect of the present invention, at least a portion of the wireless devices may comprise impulse radio devices. In an additional aspect of the present invention, the sufficient number of wireless devices with known locations may comprise three or more wireless devices with known locations. In another aspect of the present invention, at least a portion of the transmitted requests may be coded.
In a further aspect of the present invention, the additional request may be re-transmitted periodically a predetermined number of times. In such an aspect, the additional request may also be re-transmitted at a higher power level if an insufficient number of responses are received in response to the previous transmissions of the additional request. In yet another aspect of the present invention, the obtained information relating to the distance between the first wireless device and the portion of the responding other wireless devices may include a calculated distance between the first wireless device and the portion of the responding other wireless devices, and a scaling factor.
In one embodiment of the present invention, the estimated location may be stored in a memory of the first wireless device. In a further embodiment of the present invention, the obtained information may also be utilized to update an internal clock of the first wireless device.
In another embodiment of the present invention, if positioning information is received from a sufficient number of wireless devices with known locations, then the location of the first wireless device may be determined utilizing just the information obtained from the wireless devices with known locations. In yet another embodiment of the present invention, the location of the first wireless device may be estimated using only the information obtained from the portion of the responding other wireless device if no positioning information is received by the first mobile wireless device from wireless devices having known locations.